body:not(.replypage) img[src*="/b/src/"],
body:not(.replypage) img[src*="/b/thumb/"] {
    filter: brightness(0%);
}

body:not(.replypage) img[src*="/b/src/"]:hover,
body:not(.replypage) img[src*="/b/thumb/"]:hover {
    filter: brightness(100%);
}